This invention relates broadly to the production of semiconductor devices, and has particular reference to a novel device for permitting the mass transfer of silicon wafers from one wafer carrier to another carrier that has different wafer spacings.
In the production of semiconductor devices and integrated circuits on thin wafers of semiconductor material such as silicon, a number of different operations under different conditions must be performed. Thus, in cleaning and coating operations greater spacing is required between the wafers than is required or desirable for furnace operations. The greater spacing enables more uniform cleaning and coating and results in more efficient drying. For furnace operations, on the other hand, the cost, time required and limited space make it desirable to space the wafers much closer together.
The wafers are supported during the production operations by racks or carriers of various known types, and from the foregoing brief description of the operations it will be apparent that the carriers must have different wafer spacings. Since the wafers cannot be handled manually after production operations have commenced, any transfer of wafers between carriers has heretofore been accomplished by operators using tweezers. This of course is a tedious task when a multiplicity of wafers is involved.
Recently, a number of the carrier manufacturers have cooperated in developing a series of standard, compatible carriers which interface with one another so that a mass transfer of the wafers can be effected by "dumping." This system, however, is not adapted for transfers between carriers with different wafer spacings and when such a transfer is required, it is usually necessary to revert to the tweezer method.
The closest prior art known to the applicants is disclosed in U.S. Pat. Nos. 3,394,819; 3,480,151; 3,486,631 and 3,534,862. These patents are in Class 211, subclasses 41 and 126 and disclose racks or carriers for wafers rather than a transfer device as disclosed herein.